Z axis setter

[revwarguy]

To zero my Z axis, I had been using a touch plate, requiring a clip to connect to the router collet (the rest of the router is insulated) and an aluminum plate. (if curious, see it at www.liming.org/cnc, page 5) This worked well until one day as I clicked Mach3 to set the Z, it touched the plate all right, and just kept right on going. Luckily I was close the the e-stop and it didn't do much damage, but it did ruin the tip of the V bit I was using. I attributed this to my own carelessness in attaching the clip, until it happened a second time - this was getting expensive. I spent some thought about how to make better electrical contact with a collet without much luck.

On the cover of winter 2009 Digital Machinist is shown another way, so I built one shown below. Works great. I built mine from aluminum (instead of steel in the magazine) but that doesn't seem to matter. Best news is the HF dial indicator is $10, unless you have a 20% coupon, in which case it's $8. The rest of the stuff is aluminum I had left over from my CNC build, and some 6-32 screws.

The way you specify the new offset height to Mach 3 is on the first time you use it, simply lower a milling bit to read zero on the dial, and then cut something and measure the resulting cut with a caliper. Once this measured height is in Mach 3, you don't need to re-cut anything - just slide it under the bit and lower it until its says zero, and click.

Anyone see a problem with this?

[shadowvoice]

OK, your solution IS tool-safe, but for me looks to be much too complicate for daily use. I can't imagine to go via that routine some 50 times a day...

[jalessi]

Revwarguy,

Is it possible to post the article for the tool setting device?

Jeff...

[revwarguy]

Hi jalessi and shadowvoice

The issue of Digital Machinist just came out - I received mine this week. At this time, you can see a picture of it at

http://www.digitalmachinist.net/comi.../contents/view

but the will probably change when the next issue comes out. If you are not a subscriber, you can ask for their current issue for free at this address. Otherwise, try a bookstore with a good rack. (of magazines, of course! )

Maybe I have described it poorly, since using it is simpler than before, not more complicated. You just slide the end of the device under the router bit, jog the bit down until the gauge reads zero, and click a button on Mach 3. Don't know how it gets any simpler - no wires to hook up. I've edited the original message to make that clearer.

[rowbare]

I like that the tool can work without using up too much of your Z height.

For greater repeatability I would suggest adding a small raised landing pad for the cutter. This would ensure that the cutter touches the beam at a consistent distance from the pivot. Also adjust your indicator so the beam is as near level as possible at the zero point.

bob

[revwarguy]

Yes, the zero point on the dial indicator is set when the beam is exactly parallel - I did this by making the drill point of the pivot in line with the beam resting on a piece of 1/2 inch material under both sides of the pivot. Then, when assembled, the same material is is put back, making the beam parallel, and then the zero point is set.

As for where the tool touches down on the beam, it appears that the further out on the beam it touches, the better accuracy would result, but the effect is very slight, so I've just been landing it within the last 1/4 inch or so of the beam. The only force holding the beam down is the spring of the dial indicator, so the forces here are very light.

[mlabruyere]

Looks interesting but too complicated for a lot of use.

I have the traditional aluminum touch-plate but my machine is grounded such that I only need the pin lead to the aluminum (no need to clip to the end mill). I also check continuity prior to z-setting by touching the plate to the end mill and confirming that Mach sees it (LED lights).

[analogman]

I am a little more of a luddite (which is strange for a CNC guy). Like your original setup, I use a piece of PCB I measured with a mic. Wrote the thickness on the PCB. Then use a meter and check for continuity. I manually jog rather than use a script. I have to subtract manually. Not real productive and doesn't work with diamond drag bits.

Mind you nearly all of my processes are cut through, so I eye-ball it most of the time. I only use the PCB when I engrave - about once a month.

[revwarguy]

Well, I did that, too. Every time I used the touch plate, I checked to touch it to the bit and see the "LED" light come on in Mach 3. For whatever reason, after doing that on two occasions when the bit lowered and finally touched, it didn't stop, but ruined a bit.

However, I don't see why it is too complicated - you slide the unit under bit, same as the touch plate, and jog it down until it reads zero, and click the mouse, then you're done. The way my touch plate worked was pretty much the same.

And, as analogman points out, it doesn't require the bit or the router to be conductive, so you can use it with a pen or probe as well.

[mlabruyere]

Hey Rev,

Don't get me wrong....your idea is ingenious and a great use of a dial indicator.

I'm a little distressed now that you said you did check the LED prior to use and you still have the issues with Mach trying to drive the bit threw the plate.....

Did you ever find the root cause?

Matthew

[BobWarfield]

Ray Livingston has complained about Mach3 being unreliable for probing. It sure would be nice if that could be tracked down and fixed.

Best,

BW

[revwarguy]

I can't really say - It worked 99% of the time. All I could attribute it to was a crummy connection of the the alligator (actually a battery clamp) used the attached picture.

This the first I've heard of Mach3 losing probe signals - whats up with that?